Rising levels of allergic asthma and eczema in North American children have Canadian scientists wondering if there is such a thing as being "too clean." "We see auto-immune diseases like asthma and eczema increasing rapidly in North American children, but we don't see the same effect in children in the developing world," says Dr. B. Brett Finlay, a Professor in the Michael Smith Laboratories at the University of British Columbia.

This has led Dr. Finlay to embark on a new project called the Impact of the Microbiota on Immune Development and Disease that will look at microbiota (a kind of bacteria or microorganism that lives in or on our body) and its potential link to auto-immune illnesses in children. Scientists will look at the increasing evidence that intestinal microbiota, the bacteria that live in our gut, has an impact on immune development and disease, including asthma and eczema.

"The so-called 'hygiene hypothesis' is the idea that we are killing off good bacteria along with bad bacteria with some of our habits, whether it is bleaching countertops or antibiotic use in early childhood," says Finlay. "If these intestinal bacteria play a role in preventing auto-immune diseases, then our desire to be ultra-clean may mean that kids aren't getting the bacteria they need to have strong immune systems later in life."

Finlay has assembled an interdisciplinary team to study the intestinal microbiota. Sequencing the microbiota populations should allow researchers to identify the various types that are living in the gut. The team will then examine mice models and track the health development of young Canadian children enrolled in the Canadian Healthy Infant Longitudinal Development Study (CHILD) in order to both better understand the role microbiota plays in the immune system, and ultimately find new information to treat asthma and other illnesses.

"It's the kind of sensitivity that genomics can bring to revealing the complex nature of our immune system that makes projects like this one so exciting," says Dr. Alan Winter, President and CEO of Genome BC, one of the funders of the project. "This type of project has relevance on an international scale, so we are excited to see BC researchers once more taking a leading role on such a critical issue."

The five year project is funded in part by the Canadian Institutes of Health Research (CIHR) and Genome BC, each contributing $1.875 million and $625,000 respectively. The initiative is part of the Canadian Microbiome Initiative, which was created to provide an opportunity for Canadian researchers to contribute to international efforts to gain an understanding of the role of the human microbiome in health and disease. The goal will be to gain a genetic understanding of the bacteria that lives in and on the human body, specifically those found orally, on the skin, the gut, nasal/lung and vaginally.

Triclosan is a chemical compound widely used in products such as antibacterial soaps, toothpaste, pens, diaper bags and medical devices. Bisphenol A (BPA) is found in many plastics and, for example, as a protective lining in food cans. Both of these chemicals are in a class of environmental toxicants called endocrine-disrupting compounds (EDCs), which are believed to negatively impact human health by mimicking or affecting hormones.

Using data from the 2003-2006 National Health and Nutrition Examination Survey, U-M researchers compared urinary BPA and triclosan with cytomegalovirus (CMV) antibody levels and diagnosis of allergies or hay fever in a sample of U.S. adults and children over age 6. Allergy and hay fever diagnosis and CMV antibodies were used as two separate markers of immune alterations.

"We found that people over age 18 with higher levels of BPA exposure had higher CMV antibody levels, which suggests their cell-mediated immune system may not be functioning properly," said Erin Rees Clayton, research investigator at the U-M School of Public Health and first author on the paper.

Researchers also found that people age 18 and under with higher levels of triclosan were more likely to report diagnosis of allergies and hay fever.

There is growing concern among the scientific community and consumer groups that these EDCs are dangerous to humans at lower levels than previously thought.

"The triclosan findings in the younger age groups may support the 'hygiene hypothesis,' which maintains living in very clean and hygienic environments may impact our exposure to micro-organisms that are beneficial for development of the immune system," said Allison Aiello, associate professor at the U-M School of Public Health and principal investigator on the study.

As an antimicrobial agent found in many household products, triclosan may play a role in changing the micro-organisms to which we are exposed in such a way that our immune system development in childhood is affected.

"It is possible that a person can be too clean for their own good," said Aiello, who is also a visiting associate professor of epidemiology at Harvard.

Previous animal studies indicate that BPA and triclosan may affect the immune system, but this is the first known study to look at exposure to BPA and triclosan as it relates to human immune function, Aiello said.

One surprise finding is that with BPA exposure, age seems to matter, said Rees Clayton. In people 18 or older, higher amounts of BPA were associated with higher CMV levels, but in people younger than 18 the reverse was true.

"This suggests the timing of the exposure to BPA and perhaps the quantity and length of time we are exposed to BPA may be affecting the immune system response," Rees Clayton said.

This is just the first step, she said, but a very important one. Going forward, researchers would like to study the long-term effects of BPA and triclosan in people to see if they can establish a causal relationship.

One limitation of the study is that it measured disease and exposure simultaneously and thus shows only part of the picture, Aiello said.

"It is possible, for example, that individuals who have an allergy are more hygienic because of their condition, and that the relationship we observed is, therefore, not causal or is an example of reverse causation," Aiello said.

Here are few products and/or ingredients you should try to stop using right now:

Ethylene-based glycol is often used as a water-soluble solvent in many cleaning agents. It's classified as an air pollutant by the EPA.

Synthetic terpenes (as opposed to the terpenes found in some essential oils) are a class of chemicals found in orange, lemon, and pine oils. They have the potential to become carcinogenic compounds when mixed with ground-level ozone.

Chlorine, often appearing in a list of ingredients as sodium hypochlorite or hypochlorite, is in too many household cleaners to count. Breathing it in is bad for your lungs and is especially risky if you already have heart or respiratory problems.

Crystalline silica is an eye and lung irritant and likely carcinogen, according to the Cancer Prevention Coalition.

Butyl cellosolve, also IDed by the Cancer Prevention Coalition as a possible carcinogen, has been tied to kidney, liver, and lymphatic problems; is an eye and skin irritant; and is toxic to newly forming and regenerating cells.

Ammonia, like many of the others in this list, is bad for the eyes, skin, and lungs. It might also burn you.

Finally, if you want to zero in on the three most dangerous products themselves, you'd do well to avoid drain, oven, and acid-based toilet bowl cleaners, according to Philip Dickey, former staff scientist at the Washington Toxics Coalition.All are corrosive and can cause both external and internal (if swallowed) burns.

Back to the Basics

There are common-sense alternatives to cleaning without chemicals. You probably have most of what you need on hand and would use them if it weren't so easy to grab a bottle and spray or pour. But we've all been seduced by the quick and easy promise of chemicals. Now that we're beginning to realize that this promise isn't worth the toxic trade-off, it's time to get back to basics. It turns out those basics are green. They also cost a whole lot less than all those colorful containers lining the cleaning-product aisle.

First up, distilled white vinegar. It's the main ingredient in many homemade cleaning recipes, including cleaners for glass, tub and tile, toilet bowls, floors, windows, drains, and mildew. This is because of its deodorizing and sanitizing properties and acidic nature, which help it dispel bacteria, germs, and mold. Vinegar works well as a fabric softener too, dissolving detergent residue and helping to wash away smells, even those wrapped up in your partner's stinky white gym socks.

Next on the list, baking soda. The folks at Arm & Hammer don't lie when they boast of their product's many uses (visit their website for a lengthy list). Because it's abrasive, use it as a scouring powder to make sinks, counters, and tubs sparkle. It takes a little extra effort on your part, but since you'll be breathing easier you might not even notice the added labor. You may already know that baking soda will absorb carpet and fridge odors; thanks to the fact that it creates a good pH level in the wash, it'll deodorize your laundry, too, as well as make it brighter.

Third, liquid castile soap. It's the sudsy base for a lot of homemade cleaning recipes. Plus, you can use it to wash your hands. Castile soap is very mild. It used to be made exclusively from olive oil, but now you'll find it made from other vegetable oils too. Unlike in other liquid soaps, you won't find any petroleum products and their associated contaminants.

On to essential oils, or concentrated plant oils. These are derived from bark, flower petals, roots, or fruits. Talk about getting back to basics: essential oils have been used for centuries for cleaning. Today you can find them online or in small vials in your local health-food store. Some are antibacterial, including cinnamon, clove, eucalyptus, lavender, lemon, lemongrass, rose, rosemary, tea tree, and thyme.

Try using lemon oil (not the commercial variety made from petroleum distillate) as furniture polish, eucalyptus to cut grease, thyme as a cleaning disinfectant. Do keep in mind that essential oils are potent and some may irritate your skin. And they are the one green-cleaning item that isn't cheap (we paid $11 each for our 1-ounce bottles), but they are concentrated -- one bottle will last you a year.

Last but not least, there's water. It's the universal solvent in many green-cleaning recipes and is much better for you than the petroleum-based solvents found in many conventional cleaners. You can't get any safer or simpler.